1. Field of the Invention
The present invention relates, in general, to wireless communication systems, and more particularly, to an apparatus, method and system for voice communication hand-off in a packet data network environment.
2. Background of the Invention
With the advent of increasingly sophisticated telecommunication networks and data networks (or equivalently, packet data networks), different types of services are increasingly available across different types of networks. For example, data transmission services are often utilized across circuit switched telecommunication networks. In addition, voice communication services are becoming increasingly available across packet data networks (or packet switched data networks), such as the internet.
For voice communication services over a packet switched data network, such as internet telephony, particular problems may arise in mobile environments. Mobile, wireless communication systems typically employ many base stations (transceivers) forming cells or cell sites, either with mobile switching centers for circuit switched communication or with routing nodes for full duplex data packet communication, to provide wireless communication throughout a given geographic region. As a mobile unit may traverse the geographic region, the communication to and from the mobile unit may occur through one or more of these base stations and routing nodes. To maintain an ongoing communication session during such transitions between base stations and switches, various hand-off methods have evolved in circuit switched networks to transfer the wireless communication to the mobile unit from one base station to another base station, while maintaining such an ongoing call or session.
In packet switched data networks, however, such hand-off methodologies are subject to competing and often diverging objectives. For example, for transmission of encoded data such as a text file or a data file, reliability of data transfer is typically more important than comparatively small transmission delays. As a consequence, during a hand-off, data transmission may be temporarily interrupted and the data buffered, followed by resumption of transmission upon completion of the hand-off and possible retransmission of any lost data. In voice communication over packet switched data networks, however, reliability is generally less important than and secondary to considerations pertinent to transmission delays, as even a very slight delay in transmission may be noticeable and result in consumer irritation and dissatisfaction, while comparatively small data losses may be unnoticeable and highly tolerable. Minimizing such transmission delays during mobile hand-offs are increasingly important for such voice communications over such data networks.
As a consequence, a need remains to provide for comparatively seamless voice communication hand-offs in mobile data networks, which do not interrupt ongoing voice communication sessions and which are relatively imperceptible to the consumer. In addition, such a wireless communication system should be reasonably efficient and capable of cost-effective implementation, eliminating or minimizing the use of additional network resources.
The wireless communication system of the present invention provides virtually seamless and imperceptible hand-offs of voice communication sessions of mobile units in a packet data network environment. The various embodiments of the present invention are reasonably efficient and capable of cost-effective implementation in existing communication equipment such as routing nodes and base stations. Moreover, the various embodiments of the present invention eliminate or minimize the use of additional network resources, while being compatible with other intelligent network devices and systems.
In accordance with the present invention, an apparatus, method and system are provided for a hand-off of a communication session in a data network. The system embodiment includes a gateway routing node, such as a global GSN, a plurality of serving routing nodes, such as serving GSNs, and a plurality of base stations (transceivers). Prior to such a hand-off, the communication session has been established previously with a mobile unit through a first base station, a first serving routing node and a gateway routing node, utilizing a first addressing context, which consists of embedded addressing layers designating the mobile unit, the first base station and the first serving routing node, for routing incoming data packets to the first base station for transmission to the mobile unit.
For the hand-off of the communication session, the gateway routing node includes instructions, when the second base station has been selected for the hand-off, to establish a second addressing context, for the mobile unit, between the gateway routing node and the second serving routing node, consisting of embedded addressing layers designating the mobile unit, the second base station and the second serving routing node, for routing of incoming data packets to the second base station. The gateway routing node then concurrently routes incoming data packets for the mobile unit to the first serving routing node utilizing the first addressing context and to the second serving routing node utilizing the second addressing context. When the mobile unit retunes to the second base station, the hand-off is complete, and the second base station includes instructions to transmit to the mobile unit current voice communication from the incoming data packets with a second addressing context and to receive outgoing voice communication from the mobile unit. Subsequent to retuning of the mobile unit to the second base station, the gateway routing node may cease to route incoming data packets for the mobile unit to the first serving routing node utilizing the first addressing context, while continuing to route incoming data packets for the mobile unit to the second serving routing node utilizing the second addressing context.
As a consequence, the communication session of the mobile unit has been handed off, seamlessly and without interruption, from the serving base station to the target base station. Such a hand-off has also occurred utilizing minimal network resources, the switch and the base stations, without involvement of other intelligent or supervisory network elements.